Coumarone has been used in the preparation of synthetic resins, e.g., coumarone-indene resins, as a mixture because of the difficulty in separating indene and coumarone by conventional techniques like fractionation or crystallization. Coumarone has found use as a comonomer in other resins and, in high purity, as a monomer which forms an optically active polymer (The Chemistry of Cationic Polymerization, P. H. Plesch, Ed., 1963, The MacMillan Company, pp 449-450).
Previous methods for obtaining high purity coumarone, such as centrifugation, distillation and crystallization of coal tar distillates have not been particularly successful, although a chromatographic separation of indene with silica gel, activated alumina or activated carbon was disclosed in U.S. Pat. No. 2,930,821. Eluents or desorbents in the process included benzenes, lower alcohols, e.g., methanol or ethanol, carbon tetrachloride or other halogenated hydrocarbons, dioxane, nitrobenzene, steam, etc.
While recent developments indicate separation of indene from mixtures, including petrochemicals, such as crude oil fractions, e.g., naphtha, naphthalene; processed mixtures, e.g., naphtha cracker pyrolysis oil; synthetically-produced mixtures, e.g., dehydrogenation or cyclization reactions containing aromatics, by a chromatographic process, indene could not be obtained in purified form free of oxygenated compounds like coumarone, coumarone derivatives, such as methyl coumarone, etc., if they were present, because coumarone is coextracted with indene. In my previous U.S. Pat. No. 4,827,077 the preferred feeds were crude oil fractions, naphtha cracker pyrolysis oil and synthetically-produced aromatic mixtures that did not contain coumarone or other oxygenated compounds. However, the process of said patent could be practiced on feeds containing indene and coumarone if a practical way of separating coumarone from the feed thereof or from the product containing coextracted coumarone and indene could be found. Thus, it is an object of this invention to provide a method for removing coumarone from indene-containing feeds or from a product comprising a mixture of coumarone and indene obtained from another separation process in which the coumarone and indene are coextracted.
It is also known that crystalline aluminosilicates or zeolites are used in adsorption separations of various mixtures in the form of agglomerates having high physical strength and attrition resistance. Methods for forming the crystalline powders into such agglomerates include the addition of an inorganic binder, generally a clay comprising a silicon dioxide and aluminum oxide, to the high purity zeolite powder in wet mixture. The blended clay zeolite mixture is extruded into cylindrical type pellets or formed into beads which are subsequently calcined in order to convert the clay to an amorphous binder of considerable mechanical strength. As binders, clays of the kaolin type or silica are generally used.
The invention herein can be practiced in fixed or moving adsorbent bed systems or in cocurrent, pulsed batch systems described in U.S. Pat. No. 4,159,284, but the preferred system for this separation is a countercurrent simulated moving bed system, such as described in Broughton U.S. Pat. No. 2,985,589, incorporated herein by reference. Cyclic advancement of the input and output streams can be accomplished by a manifolding system, which are also known, e.g., by rotary disc valves shown in U.S. Pat. Nos. 3,040,777 and 3,422,848. Equipment utilizing these principles are familiar, in sizes ranging from pilot plant scale (deRosset U.S. Pat. No. 3,706,812) to commercial scale in flow rates from a few cc per hour to many thousands of gallons per hour.
The functions and properties of adsorbents and desorbents in the chromatographic separation of liquid components are well-known, but for reference thereto, Zinnen et al U.S. Pat. No. 4,642,397 is incorporated herein.
It is a further object of this invention to obtain coumarone in highly purified form by a highly selective chromatographic adsorption separation process from coumarone-indene mixtures, such as coal tar distillates.
It is a further object to provide a desorbent which will selectively desorb the coumarone from the adsorbent with sufficient resolution so as to obtain coumarone product with substantially reduced impurities and other feed materials. The preferred desorbents are ketones, esters and alcohols having a boiling point differing from the boiling range of the feed by at least about 5.degree. C.
Other objects of the invention will be apparent from the following discussion.